This invention relates generally to an axial piston pump and more specifically to a swashplate arrangement for an axial piston pump.
Variable displacement axial piston pumps are well known in the art and typically include a barrel having a plurality of piston assemblies slideably disposed in respective bores within the barrel and a swashplate that is in mating contact with the piston assemblies so that the piston assemblies are forced to reciprocate within the bores of the barrel to receive fluid therein and discharge fluid therefrom. The swashplate is secured to the housing of the pump and is selectively pivotable relative to the barrel so that the volume of fluid being discharged therefrom may be controlled. There has been many attempts to control the pressure transition between the point at which all of the fluid has been discharged from the respective bores and the point at which the respective bores are opened to receive more fluid. Likewise, there has been many attempts to control the pressure transition between the point at which the respective bores are full and the point at which respective bores are opended to discharge fluid. In most of these attempts, special slots or holes are provided to controllably interconnect the high pressure side of the pump to the low pressure side and vice-versa to make the pressure transition as smooth as possible. Even with the special slots or holes, energy is wasted during the respective pressure transitions.
Another example of an axial piston pump attempts to provide a new neutral control of the swashplate. In this arrangement, the swashplate assembly has a primary swashplate that is rotated in a well known manner and a thrust plate is permitted to freely pivot in a 360 degree arc relative to the primary swashplate for a small, predefined distance. This permits the pump to rely on its internal swivel forces to move the thrust plate to a non-fluid discharging mode anytime the swashplate is near its zero position. Such an arrangement is set forth in U.S. Pat. No. 4,825,753, issued May 2, 1989 and assigned to Kayaba Industry Co.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a variable displacement axial piston pump is adapted for use in a fluid system. The variable displacement axial piston pump includes a housing, a rotating group, and a swashplate arrangement. The housing has a body portion and a head portion with an inlet port passage and an outlet port passage. The rotating group is disposed in the body portion and has an axis of rotation. The rotating group includes a barrel having a plurality of cylinder bores and a plurality of piston assemblies with each of the plurality of piston assemblies having a piston slideably disposed within one of the cylinder bores and a shoe pivotably attached to and extending from the piston. The barrel of the rotating group is in fluid communication with the inlet and outlet port passages of the housing head portion. The swashplate arrangement is disposed in the body portion and is pivotable in a first arcuate direction relative to the axis of rotation of the barrel and pivotable in a second arcuate direction in response to various system parameters.
In another aspect of the subject invention, a method of controlling pressure transitions is provided within a variable displacement axial piston pump between its inlet passage and its outlet passage. The method includes providing a rotating group having an axis of rotation, providing a swashplate arrangement pivotable in a first arcuate direction relative to the axis of rotation of the rotating group and pivotable in a second arcuate direction in response to various system parameters.